Expected return and standard deviation explained in this answer

The probability that the economy will contract is 0.2. The probability of moderate growth is 0.6 and the probability of a rapid expansion is 0.2. If the economy contracts, you can expect a return on your portfolio of 5 percent. With moderate growth, your return will be 8 percent. If there is a rapid expansion, your portfolio will return 15 percent.

What is your expected return?
What is the standard deviation of the return?

Need computations please to help me understand. For study purposes only